The present invention relates to component mounting method and apparatus for mounting, for example, a component such as an electronic, mechanical, or optical component to a specified position on an object to be mounted such as a printed circuit board. More particularly, the invention relates to component mounting method and apparatus which make it possible to mount the component on the object with high precision, by driving a rotating mechanism so that the component will be rotated in one direction, with a view to suppressing the occurrence of lost motions of the rotating mechanism in correcting the postural angle of the component during the mounting operation.
FIG. 14 is a perspective view of a conventional electronic component mounting apparatus 100 for mounting electronic components. A conveyor 132 conveys circuit boards to and from the electronic component mounting apparatus 100, and further holds the circuit boards during production. Electronic component feeders 133 and 134 store and feed electronic components to be mounted on the circuit boards. The electronic component feeder 133 is a reel type electronic component feeder in which electronic components are stored on a reel, and the electronic component feeder 134 is a tray type electronic component feeder in which electronic components are stored on a tray. A component pickup head 136, which is equipped with a nozzle 138 for picking up an electronic component from the electronic component feeders 133, 134, performs up and down motions, rotating motion and other motions of the nozzle 138. The rotating motion is effected by a rotating mechanism connected to the component pickup head 136. The component pickup head 136 is provided with a second component recognition camera 11 for capturing an image of the electronic component from above. A component recognition camera 137 is provided for capturing, from below, an image of the posture of the electronic component picked up by the nozzle 138. An X-Y robot 135 moves the component pickup head 136 in X and Y directions.
The electronic component mounting apparatus 100 performs the following operations. For picking up an electronic component, the X-Y robot 135 moves the component pickup head 136, i.e. the nozzle 138, to an electronic-component pickup position in the electronic component feeder 133 or 134 and then lowers the nozzle 138 to pick up an electronic component. The nozzle 138 is lifted after the pickup.
Next, as shown at Step (“S” in the drawings) 101 of FIG. 16, the nozzle 138, after picking up the electronic component, is rotated by the rotating mechanism circumferentially of the nozzle 138 about the center axis of the nozzle 138, according to a mounting angle preset for the picked-up electronic component. Subsequently, at Step 102, the X-Y robot 135 moves the component pickup head 136 to the location of the component recognition camera 137, where the posture of the electronic component picked up by the nozzle 138 is recognized by the component recognition camera 137. Next, at Step 103, a difference between the actual angle of the picked-up electronic component and the mounting angle is determined based on the recognition result, and an angular correction for the picked-up electronic component is performed so that the difference value becomes zero. This correction is performed by rotating the nozzle 138, which is effected by again driving the rotating mechanism. Then, at Step 104, the electronic component, picked up by the nozzle 138, is moved to a specified position on the electronic circuit board in the X-and Y-directions by the component pickup head 136, which is moved by the X-Y robot 135. Further with an operation of the component pickup head 136, the nozzle 138 is lowered so that the electronic component is mounted to the specified component mounting position-on the electronic circuit board, where the electronic component is released from the, pickup head. By iterating these operations, electronic components are removed one after another from the electronic component feeder 133 or 134 and mounted onto the electronic circuit board.
The aforementioned rotating mechanism for the nozzle 138 is shown in FIG. 15. The nozzle 138 is fixed to a gear 102 so as to be inserted through center part of the gear 102. The gear 102 is connected to a motor output shaft 105 via a timing belt 101. Accordingly, rotation of the output shaft 105 is transferred to the pickup nozzle 138 via the gear 102 by the timing belt 101, by which the electronic component picked up by the pickup nozzle 138 is rotated to the specified mounting angle.
However, the timing belt 101 or the gear 102 has a backlash. Moreover, depending on whether the angle of the electronic component is too large or too small relative to the target mounting angle, the direction in which the nozzle 138 is rotated differs. Therefore, by rotating the nozzle 138 clockwise, or counterclockwise, or clockwise and counterclockwise together with the gear 102 or the like, there can occur an error in the final mounting angle of the electronic component due to the backlash.
To suppress the occurrence of such errors, the resolution of the timing belt 101 or the gear 102 is enhanced or a mechanism which directly, transforms rotation of the motor output shaft into rotation of the pickup nozzle is adopted, responsive to the required precision. However, this increases the manufacturing cost, and requires a large space for the installation of the motor and the nozzle 138.